In Theory vs luapsel
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
In Theory
This app provides a unique interval-based MIDI keyboard with over 110 scales. It allows for flexible chord creation by toggling additional intervals and notes from different octaves. It integrates with external MIDI keyboards and sequencers for advanced music production.
- Interval-based MIDI keyboard
- Over 110 built-in scales
- Customizable chord voicing
- MIDI keyboard input support
- MIDI CC message control
- AUv3 plugin compatibility
- Visual scale and note display
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In Theory is an interval based MIDI keyboard app with more than 110 scales. It has a keypad at the bottom with the interval buttons like +2, +1, 0, -1, -2 which would change the current note. Zero means the current note, +1 means the note after the current note, +2 means two notes after the current note, -2 means two notes before the current note in the scale and so on. Above the keypad, you can toggle additional intervals in the scale for creating chord voices. You can also select the notes from an octave above and an octave below for creating rich, extended chords. You can use your MIDI keyboard to play In Theory as well. The middle C4 key on your MIDI keyboard triggers the 0 (zero) button on the app's keypad. The white notes after the C4 note would trigger the positive buttons, the white notes before the C4 note would trigger the negative notes on the keypad. You can also toggle the chord intervals with MIDI CC messages. You can set a MIDI CC number and a MIDI Channel for toggling the chord intervals from the settings menu. If you send a MIDI CC value between 0-62, you can toggle the chord intervals respectively. With the MIDI capabilities, you can also sequence the app with a MIDI sequencer app like PolyBud, ShiftBud, MelodyBud etc. In Theory has more than 110 scales built-in. You can also use the custom scales you made in ScaleBud 2 app as well. The key and scale could be changed externally from a MIDI controller in AUv3 plugin with the AU parameters. The circular display on the UI will show you where you are in the scale. Also, when you play a note, you will see the every playing note on the screen with the root note and the chord intervals. Please note that In Theory is a MIDI app and does not produce any kind of sound on its own. You need to connect the MIDI output of the app to an audio app's MIDI input. For the AUv3 plugin you'll need an AUv3 host app such as AUM, Cubase, Nanostudio, apeMatrix etc.
luapsel
Create calming electric guitar ambience with reversed samples and built-in effects. Offers polyphonic playback, multiple articulations, and real-time sound shaping tools for unique musical textures.
- Polyphonic reversed guitar sounds
- Round Robin sampling
- Multiple articulations
- Built-in delay, reverb, chorus
- Real-time low-pass filter
- ADSR Release control
- Standalone samples available
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luapsel: Unique Evolving Electric Guitar Ambience luapsel is a collection of Electric Guitar samples, meticulously multi-sampled in Round Robin and reversed in the most transparent way possible to offer your projects an easy-to-use calming vibe. Play around with built-in delay, reverb, and chorus effects, or go au naturel. Sound design is a breeze with real-time filters, release control, and tuning options. Get luapsel for free inside Decent Sampler or just enjoy the raw samples, or grab the new improved app for just $1. Features -Polyphonic reversed guitar sounds -Round Robin sampling for nuanced playback -Four articulations: Original, Looped, Fast, & Slow -Built-in delay, reverb, and chorus effects -Real-time low-pass filter (Tone) -ADSR Release control and real-time sampling tuning -Available for Decent Sampler or as standalone samples
Screenshots
Verdict
The clearest difference is rating: In Theory at 5.0 against luapsel's 4.5. luapsel's advantage is price ($0.99 vs $4.99). On ratings volume, update cadence, ads and in-app purchases there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
In Theory costs $4.99 and luapsel $0.99 up front. Neither carries in-app purchases, so what you see is what you pay.
In Theory holds the better App Store score, 5.0 against 4.5. Both are backed by a comparable volume of ratings — 4 and 4 respectively.
In Theory ships an update weekly, luapsel every 6 days. Both last shipped on October 24, 2026.
| Parameter | In Theory | luapsel |
|---|---|---|
| Price | $4.99 | $0.99 — better |
| Rating | 5.0 (4 ratings) — better | 4.5 (4 ratings) |
| Positive reviews | 100.0% of reviews | — |
| Number of ratings | 4 | 4 |
| Update frequency | Weekly | Every 6 days — better |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Paid | Paid |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Requires iOS | 13.0 | 12.0 — better |
| Further details — not scored | ||
| Size | 7 MB | 101 MB |
| Age rating | 4+ | 4+ |
| Developer | Cem Olcay | OSC Audio |
Customer experience
In Theory
luapsel
In-app purchases
In Theory
No in-app purchases
luapsel
No in-app purchases









